put out any naked lights (flames), eg your hob or candles. Don't smoke, strike matches or do anything that could cause ignition

open any electric doors or gates manually

Carbon monoxide poisoning

Carbon monoxide is an odourless, colourless gas and exposure to it can be fatal. It's produced when products containing carbon, typically fossil fuels, are burnt without enough oxygen.

To prevent this, boilers and central heating systems need regular servicing. A carbon monoxide detector - although not an alternative to regular servicing - will monitor the area it's fitted in and provide an early warning if something is wrong.